Definition:

struct __drm_i915_gem_create_ext {    __u64 size;    __u32 handle;#define I915_GEM_CREATE_EXT_FLAG_NEEDS_CPU_ACCESS (1 << 0);    __u32 flags;#define I915_GEM_CREATE_EXT_MEMORY_REGIONS 0;#define I915_GEM_CREATE_EXT_PROTECTED_CONTENT 1;    __u64 extensions;};

Members

size

Requested size for the object.

The (page-aligned) allocated size for the object will be returned.

Note that for some devices we have might have further minimumpage-size restrictions (larger than 4K), like for device local-memory.However in general the final size here should always reflect anyrounding up, if for example using the I915_GEM_CREATE_EXT_MEMORY_REGIONSextension to place the object in device local-memory. The kernel willalways select the largest minimum page-size for the set of possibleplacements as the value to use when rounding up thesize.

handle

Returned handle for the object.

Object handles are nonzero.

flags

Optional flags.

Supported values:

I915_GEM_CREATE_EXT_FLAG_NEEDS_CPU_ACCESS - Signal to the kernel thatthe object will need to be accessed via the CPU.

Only valid when placing objects in I915_MEMORY_CLASS_DEVICE, and onlystrictly required on configurations where some subset of the devicememory is directly visible/mappable through the CPU (which we alsocall small BAR), like on some DG2+ systems. Note that this is quiteundesirable, but due to various factors like the client CPU, BIOS etcit’s something we can expect to see in the wild. See__drm_i915_memory_region_info.probed_cpu_visible_size for how todetermine if this system applies.

Note that one of the placements MUST be I915_MEMORY_CLASS_SYSTEM, toensure the kernel can always spill the allocation to system memory,if the object can’t be allocated in the mappable part ofI915_MEMORY_CLASS_DEVICE.

Also note that since the kernel only supports flat-CCS on objectsthat canonly be placed in I915_MEMORY_CLASS_DEVICE, we thereforedon’t support I915_GEM_CREATE_EXT_FLAG_NEEDS_CPU_ACCESS together withflat-CCS.

Without this hint, the kernel will assume that non-mappableI915_MEMORY_CLASS_DEVICE is preferred for this object. Note that thekernel can still migrate the object to the mappable part, as a lastresort, if userspace ever CPU faults this object, but this might beexpensive, and so ideally should be avoided.

On older kernels which lack the relevant small-bar uAPI support (seealso__drm_i915_memory_region_info.probed_cpu_visible_size),usage of the flag will result in an error, but it should NEVER bepossible to end up with a small BAR configuration, assuming we canalso successfully load the i915 kernel module. In such cases theentire I915_MEMORY_CLASS_DEVICE region will be CPU accessible, and assuch there are zero restrictions on where the object can be placed.

extensions

The chain of extensions to apply to this object.

This will be useful in the future when we need to support severaldifferent extensions, and we need to apply more than one whencreating the object. Seestructi915_user_extension.

If we don’t supply any extensions then we get the same old gem_createbehaviour.

For I915_GEM_CREATE_EXT_MEMORY_REGIONS usage seestructdrm_i915_gem_create_ext_memory_regions.

For I915_GEM_CREATE_EXT_PROTECTED_CONTENT usage seestructdrm_i915_gem_create_ext_protected_content.

Definition:

struct __drm_i915_memory_region_info {    struct drm_i915_gem_memory_class_instance region;    __u32 rsvd0;    __u64 probed_size;    __u64 unallocated_size;    union {        __u64 rsvd1[8];        struct {            __u64 probed_cpu_visible_size;            __u64 unallocated_cpu_visible_size;        };    };};

Members

region

The class:instance pair encoding

rsvd0

MBZ

probed_size

Memory probed by the driver

Note that it should not be possible to ever encounter a zero valuehere, also note that no current region type will ever return -1 here.Although for future region types, this might be a possibility. Thesame applies to the other size fields.

unallocated_size

Estimate of memory remaining

Requires CAP_PERFMON or CAP_SYS_ADMIN to get reliable accounting.Without this (or if this is an older kernel) the value here willalways equal theprobed_size. Note this is only currently trackedfor I915_MEMORY_CLASS_DEVICE regions (for other types the value herewill always equal theprobed_size).

{unnamed_union}

anonymous

rsvd1

MBZ

{unnamed_struct}

anonymous

probed_cpu_visible_size

Memory probed by the driverthat is CPU accessible.

This will be always be <=probed_size, and theremainder (if there is any) will not be CPUaccessible.

On systems without small BAR, theprobed_size willalways equal theprobed_cpu_visible_size, since allof it will be CPU accessible.

Note this is only tracked forI915_MEMORY_CLASS_DEVICE regions (for other types thevalue here will always equal theprobed_size).

Note that if the value returned here is zero, thenthis must be an old kernel which lacks the relevantsmall-bar uAPI support (includingI915_GEM_CREATE_EXT_FLAG_NEEDS_CPU_ACCESS), but onsuch systems we should never actually end up with asmall BAR configuration, assuming we are able to loadthe kernel module. Hence it should be safe to treatthis the same as whenprobed_cpu_visible_size ==probed_size.

unallocated_cpu_visible_size

Estimate of CPUvisible memory remaining

Note this is only tracked forI915_MEMORY_CLASS_DEVICE regions (for other types thevalue here will always equal theprobed_cpu_visible_size).

Requires CAP_PERFMON or CAP_SYS_ADMIN to get reliableaccounting. Without this the value here will alwaysequal theprobed_cpu_visible_size. Note this is onlycurrently tracked for I915_MEMORY_CLASS_DEVICEregions (for other types the value here will alsoalways equal theprobed_cpu_visible_size).

If this is an older kernel the value here will bezero, see alsoprobed_cpu_visible_size.